The present invention concerns safety syringes for medical uses which permit the limitation and if possible the avoidance of injury to healthcare workers. The aim of these safety syringes is evidently to avoid risk of contamination during handling of the syringe and to prevent the needle, after administering an injection into a patient suffering from an illness such as viral hepatatis or AIDS, from injuring the nurse before the needle has been safely protected
Such safety syringes are known in documents WO 90/06148, EP 0.326.983, EP 0.347.742, U.S. Pat. No. 4,507,177 or U.S. Pat. No. 4,675,005. All of the syringes described in these documents necessitate the retracting of the needle into the syringe barrel after use, but by complicated manipulations involving rotary movements, coupling by bayonet etc. which are impractical movements which hospital personnel are not used to carrying out and which require the use of two hands, one of which can approach the sharp tip of an infected needle.
The aim of the present invention is to create a safety syringe for medical use permitting the needle to be retracted inside the cylinder after use but which can be utilized in the same way as all standard syringes for its preparation and use, that is to say fixing the required needle, filling, changing needle if necessary, coupling onto an air filter if necessary, evacuation of air-bubbles and injection. Nevertheless, the difference and the advantage compared to standard syringes is that the operator""s hands cannot approach the dangerous distal zone of the syringe which is a source of injury because it is obligatory that the active hand which pulls the piston is occupied at the proximal extremity of the syringe.
Another aim of the invention is to prevent the user to try to re-cap the infected needle or to have to dispose of this needle in a specialized disposal box which is not always handy. Yet another aim is to facilitate the reading of the volume of liquid introduced through the needle.
Another aim of the present invention is the creation of a purely mechanical syringe having a small number of parts, easy to manufacture and at low cost compared to other known safety syringes, and with a cost comparable to existing low-cost standard single-use syringes.
Another aim of the present invention is the creation of a safety syringe which allows the user, before employing the syringe, to choose the appropriate standard needle and to fix it onto the syringe the same as with low-cost conventional single use syringes, which is often not possible with safety syringes.
The objective of the present invention is a safety syringe which avoids the disadvantages of existing syringes permitting the above mentioned aims to be reached, comprising a barrel, a plunger which can be moved linearly and remain watertight and a needle carrier similarly movable linearly inside the barrel and which distinguishes itself by the characteristics listed in claim 1.